The present invention relates to a thrust reverser for a tubojet engine in which pivotable thrust reverser doors have hinged front and rear door portions.
Turbofan-type turbojet engines are well-known in the art and typically comprise an annular cowling concentrically arranged around the turbojet engine housing to form an annular cold flow air duct. A fan driven by the turbojet engine is located in the forward portion of the cold flow air duct to force air through the duct and to augment the thrust of the turbojet engine. The cold flow air duct may extend substantially along the length of the turbojet engine in which case the downstream or rear portion of the cowling acts as an outer boundary for both the cold flow air and the hot exhaust gases from the turbojet engine, or, alternatively, the cowling forming the outer boundary of the cold flow duct may be significantly shorter than the overall length of turbojet engine. It is known in the art to provide pivoting thrust reverser doors on the cowling forming the outer boundary of the cold flow air duct. If the turbojet engine is located externally of an aircraft, the outer surface of the cowling forms an aerodynamic surface to minimize the drag of the engine cowling.
FIG. 1 illustrates a typical prior art pivoting door type thrust reverser in cross-section, while FIG. 2 is a perspective representation of a cowling incorporating the known thrust reverser doors illustrated in FIG. 1. The cowling has a front cowling portion 1 and may have a rear cowling portion 3 which define between them an opening through the cowling which is normally blocked by a thrust reverser 2. The thrust reverser 2 comprises a door 7 pivotally attached to the cowling so as to be movable between forward thrust positions (illustrated in FIG. 1) and reverse thrust positions. The movement of the thrust reverser door 7 is controlled by actuator 8 which is attached to internal structure 6 of the cowling 1 and which has an extendible and retractable piston rod connected to the internal structure of the thrust reverser door 7. When in the forward thrust position, the thrust reverser door 7 has an outer surface 9 that is substantially flush with the outer surface of the cowling 1 and an inner surface 11 which forms a portion of the outer boundary of the cold flow gas duct. A deflector 13 may be attached to the front edge portion of the thrust reverser door 7 to impart a forward direction to the gases when the thrust reverser door 7 is in the reverse thrust position. As best illustrated in FIG. 2, the cowling 1 may have a plurality of thrust reverser doors 7 each pivotally attached to longitudinal portions 18 of the cowling which extend between adjacent doors. The longitudinally extending portions 18 of the cowling extend rearwardly from a front portion 4 of the cowling 1. The front portion of the inner surface 11 of the thrust reverser door 7 may be tapered so as to provide a more effective direction of the gases when in the reverse thrust position. However, when the thrust reverser door is in the forward thrust position, this surface may form a cavity 16 which will slightly degrade the efficiency of the engine by creating perturbations within the annular gas flow duct.
In the reverse thrust position, the front portion of the thrust reverser door 7 will move radially outwardly from the cowling 1 while the rear portion moves radially inwardly into the gas flow duct. The rear portion of the thrust reverser door 7 blocks at least a portion of the annular gas flow duct so as to redirect the gases outwardly through the cowling. The configuration of the inner surface 11 coupled with the deflector 13 impart to these gases a forward direction which provides a reverse thrust to the aircraft structure. Typical examples of such thrust reverses are illustrated in French Patents 1,482,538 and 2 030 034.
U.S. Pat. No. 3,605,411 illustrates a pivoting door thrust reversing system in which the forward deflector 13 is movably affixed to the thrust reverser door so as to extend therefrom when the door is in the reverse thrust position and to retract when the door is in the forward thrust position. Another example of a system incorporating movable deflectors can be found in French Patent 2 618 853. French Patent 2 680 547 illustrates a pivoting door thrust reverser system utilizing a combination of deflectors and deflection edges to optimize the gas flow direction when the thrust reverser door is in the reverse thrust position.
It is known to move the thrust reverser doors between the forward and reverse thrust positions using an actuator as illustrated in FIG. 1 and as illustrated in French Patent 1,482,538.
Although generally successful, the known pivoting door type thrust reversers have suffered from the drawback of being urged to their reverse thrust positions by the forces exerted on the inner surfaces of the doors by the pressurized gases within the gas flow duct. Although the known thrust reversers incorporate various locking and latching mechanisms to lock and latch the doors in their forward thrust positions, the failure or malfunction of such locking and latching systems may result in the doors being inadvertently deployed to their reverse thrust positions due to the action of the pressurized gases within the gas flow duct. The total cross-section of the openings through the cowling must be larger than the cross-section of the gas flow duct taken in a plane located upstream of the cowling openings. In accommodating the dimensions required of the thrust reverser doors the effect of the internal gas pressure on the doors is such that very high stresses are passed through the actuator requiring a strong actuator attachment which, in turn, increases the weight of the cowling assembly. The use of sufficiently heavy locking and latching systems also increase the weight of the engine assembly.